@@ -12,24 +12,48 @@ import (
1212)
1313
1414var (
15- mimeLock sync.RWMutex // guards following 3 maps
16- mimeTypes map [string ]string // ".Z" => "application/x-compress"
17- mimeTypesLower map [string ]string // ".z" => "application/x-compress"
15+ mimeTypes sync.Map // map[string]string; ".Z" => "application/x-compress"
16+ mimeTypesLower sync.Map // map[string]string; ".z" => "application/x-compress"
1817
1918 // extensions maps from MIME type to list of lowercase file
2019 // extensions: "image/jpeg" => [".jpg", ".jpeg"]
21- extensions map [string ][]string
20+ extensionsMu sync.Mutex // Guards stores (but not loads) on extensions.
21+ extensions sync.Map // map[string][]string; slice values are append-only.
2222)
2323
24+ func clearSyncMap (m * sync.Map ) {
25+ m .Range (func (k , _ interface {}) bool {
26+ m .Delete (k )
27+ return true
28+ })
29+ }
30+
2431// setMimeTypes is used by initMime's non-test path, and by tests.
25- // The two maps must not be the same, or nil.
2632func setMimeTypes (lowerExt , mixExt map [string ]string ) {
27- if lowerExt == nil || mixExt == nil {
28- panic ("nil map" )
33+ clearSyncMap (& mimeTypes )
34+ clearSyncMap (& mimeTypesLower )
35+ clearSyncMap (& extensions )
36+
37+ for k , v := range lowerExt {
38+ mimeTypesLower .Store (k , v )
39+ }
40+ for k , v := range mixExt {
41+ mimeTypes .Store (k , v )
42+ }
43+
44+ extensionsMu .Lock ()
45+ defer extensionsMu .Unlock ()
46+ for k , v := range lowerExt {
47+ justType , _ , err := ParseMediaType (v )
48+ if err != nil {
49+ panic (err )
50+ }
51+ var exts []string
52+ if ei , ok := extensions .Load (k ); ok {
53+ exts = ei .([]string )
54+ }
55+ extensions .Store (justType , append (exts , k ))
2956 }
30- mimeTypesLower = lowerExt
31- mimeTypes = mixExt
32- extensions = invert (lowerExt )
3357}
3458
3559var builtinTypesLower = map [string ]string {
@@ -45,29 +69,6 @@ var builtinTypesLower = map[string]string{
4569 ".xml" : "text/xml; charset=utf-8" ,
4670}
4771
48- func clone (m map [string ]string ) map [string ]string {
49- m2 := make (map [string ]string , len (m ))
50- for k , v := range m {
51- m2 [k ] = v
52- if strings .ToLower (k ) != k {
53- panic ("keys in builtinTypesLower must be lowercase" )
54- }
55- }
56- return m2
57- }
58-
59- func invert (m map [string ]string ) map [string ][]string {
60- m2 := make (map [string ][]string , len (m ))
61- for k , v := range m {
62- justType , _ , err := ParseMediaType (v )
63- if err != nil {
64- panic (err )
65- }
66- m2 [justType ] = append (m2 [justType ], k )
67- }
68- return m2
69- }
70-
7172var once sync.Once // guards initMime
7273
7374var testInitMime , osInitMime func ()
@@ -76,7 +77,7 @@ func initMime() {
7677 if fn := testInitMime ; fn != nil {
7778 fn ()
7879 } else {
79- setMimeTypes (builtinTypesLower , clone ( builtinTypesLower ) )
80+ setMimeTypes (builtinTypesLower , builtinTypesLower )
8081 osInitMime ()
8182 }
8283}
@@ -100,12 +101,10 @@ func initMime() {
100101// Text types have the charset parameter set to "utf-8" by default.
101102func TypeByExtension (ext string ) string {
102103 once .Do (initMime )
103- mimeLock .RLock ()
104- defer mimeLock .RUnlock ()
105104
106105 // Case-sensitive lookup.
107- if v := mimeTypes [ ext ]; v != "" {
108- return v
106+ if v , ok := mimeTypes . Load ( ext ); ok {
107+ return v .( string )
109108 }
110109
111110 // Case-insensitive lookup.
@@ -118,17 +117,19 @@ func TypeByExtension(ext string) string {
118117 c := ext [i ]
119118 if c >= utf8RuneSelf {
120119 // Slow path.
121- return mimeTypesLower [strings .ToLower (ext )]
120+ si , _ := mimeTypesLower .Load (strings .ToLower (ext ))
121+ s , _ := si .(string )
122+ return s
122123 }
123124 if 'A' <= c && c <= 'Z' {
124125 lower = append (lower , c + ('a' - 'A' ))
125126 } else {
126127 lower = append (lower , c )
127128 }
128129 }
129- // The conversion from []byte to string doesn't allocate in
130- // a map lookup.
131- return mimeTypesLower [ string ( lower )]
130+ si , _ := mimeTypesLower . Load ( string ( lower ))
131+ s , _ := si .( string )
132+ return s
132133}
133134
134135// ExtensionsByType returns the extensions known to be associated with the MIME
@@ -142,13 +143,11 @@ func ExtensionsByType(typ string) ([]string, error) {
142143 }
143144
144145 once .Do (initMime )
145- mimeLock .RLock ()
146- defer mimeLock .RUnlock ()
147- s , ok := extensions [justType ]
146+ s , ok := extensions .Load (justType )
148147 if ! ok {
149148 return nil , nil
150149 }
151- return append ([]string {}, s ... ), nil
150+ return append ([]string {}, s .([] string ) . ..nil
152151}
153152
154153// AddExtensionType sets the MIME type associated with
@@ -173,15 +172,20 @@ func setExtensionType(extension, mimeType string) error {
173172 }
174173 extLower := strings .ToLower (extension )
175174
176- mimeLock .Lock ()
177- defer mimeLock .Unlock ()
178- mimeTypes [extension ] = mimeType
179- mimeTypesLower [extLower ] = mimeType
180- for _ , v := range extensions [justType ] {
175+ mimeTypes .Store (extension , mimeType )
176+ mimeTypesLower .Store (extLower , mimeType )
177+
178+ extensionsMu .Lock ()
179+ defer extensionsMu .Unlock ()
180+ var exts []string
181+ if ei , ok := extensions .Load (justType ); ok {
182+ exts = ei .([]string )
183+ }
184+ for _ , v := range exts {
181185 if v == extLower {
182186 return nil
183187 }
184188 }
185- extensions [ justType ] = append (extensions [ justType ] , extLower )
189+ extensions . Store ( justType , append (exts , extLower ) )
186190 return nil
187191}
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